The present invention relates to a novel trailer structure and in particular to a trailer having means for automatically retracting the lower portion of the front undercarriage of the trailer when the trailer is coupled to a tractor.
Conventional trailer designs typically include an upper fifth wheel located at the forward end of the trailer that is adapted to be supported by the lower fifth wheel of a tractor when the trailer is coupled to the tractor. When uncoupled from the tractor, the forward end of the trailer is supported by a front undercarriage, commonly referred to as landing gear, which is adapted to be raised or retracted in some manner when the trailer is coupled to the tractor for service.
Several designs have been proposed to automatically retract the landing gear of a trailer as the tractor is backed up and coupled to the trailer. However, such designs have generally sought to retract the entire landing gear assembly, which typically requires relatively costly and in some cases fairly complex mechanisms. This is due primarily to the increased structural integrity required of the components in the operating mechanism as well as the resulting additional complexity in the entire retractable undercarriage assembly.
The present invention seeks to minimize the expense and complexity of automatic retractable landing gear assemblies by providing a trailer designs having an undercarriage comprised of fixed support legs with pivotal lower "feet" members that are adapted to be automatically retracted when the trailer is coupled to a tractor. By retracting only the lower portion of the front undercarriage supports, the fixed upper support struts can be rigidly secured to the bed of the trailer in a substantially less expensive manner than if the entire undercarriage assembly were designed to be retractable. In addition, the relative simplicity of the design greatly improves long term reliability of the system which in the past has proven to be a significant problem in view of the harsh environment to which the undercarriage of the trailer is exposed.
In general, the automatic retracting mechanism of the present invention includes a rotatable cam plate member that is adapted to be actuated by the kingpin on the fifth wheel of the tractor. In particular, as the tractor is backed up to the trailer, the kingpin is guided along a slot located at the front end of the trailer and into the "jaw" of the cam plate member. The rearward movement of the kingpin actuates the cam plate causing it to rotate about its pivot point. The rotation of the cam plate is translated into a fore or aft movement of a longitudinal rod that is affixed at one end to the cam plate and at its other end to a pair of transverse supporting links connected to the feet of the undercarriage assembly. Aft movement of the longitudinal connecting rod serves to draw the transverse links inwardly with respect to the sides of the trailer, thereby folding the feet of the undercarriage assembly inwardly to their retracted transport position. In addition, a latching mechanism is provided that is adapted to automatically lock the kingpin of the tractor to the cam plate of the trailer when the tractor is completely coupled to the trailer.
To uncouple the tractor from the trailer, a manually actuated unlatching mechanism is provided at the front of the trailer that is adapted to unlock the kingpin from the cam plate and hold the latching mechanism in the unlocked condition to permit the tractor to be disengaged from the trailer. As the tractor is driven away from the trailer, the forward movement of the kingpin causes the cam plate to rotate back to its original position, which in turn causes forward movement of the longitudinal connecting rod which actuates the transverse links to lower the feet of the front undercarriage.
Additional objects and advantages of the present invention will become apparent from a reading of the detailed description of the preferred embodiment which makes reference to the following set of drawings in which :